N-arylsulfonyl p-aminobenzoyl glutamates



United States Patent 6 N -ARYLSULFONYL p-AMINOBENZOYL GLUTAMATES David I. Weisblat, Barney J. Magerlein, Donald R. Myers, and Stanley T. Rolfsou, Kalamazoo, Mich., assiguors to The Upjohn Company, Kalamazoo, Mich., a corporation of Michigan No Drawing. Application July 31, 1948, Serial No. 41,888

8 Claims. (Cl. 260-470) This invention relates to glutamic acid compounds, particularly to certain glutamic acid compounds substituted in the amino group, and to intermediate compounds and methods useful in their preparation.

The compounds of the invention are the N'-(arylsulfonyl-p-aminobenzoyl)-glutamic acid compounds comprising the N-(arylsulfonyl-p-aminobenzoyl)-glutamic acids, the N-(arylsulfonyl-p-aminobenzoyl)-glutamylglutamic acids and the alkyl esters thereof having the generic formula N-(arylsulfonyl-p-aminobenzoyl)glutamic acid compounds wherein R is from the group consisting of hydrogen and the alkyl radicals, Z is an arylsulfonyl radical and n is from the group consisting of the integers 1 to 7, inclusive.

In the naming of compounds of the invention the nitrogen atom of the glutamic acid residue is, for convenience, herein referred to by the symbol N and the nitrogen atom of the p-aminobenzoic acid residue is referred to by the symbol N.

As indicated by the formula given, compounds containing more than one glutamic acid or ester residue contemplated by the invention are those wherein only the gamma-carboxyl groups are involved in the peptide linkages, such as residues derived from N- (p-aminbenzoyl)- gamma-glutamylglutamic acid, N'-(p-aminobenzoyl)- gamma-glutamyl-gamma-glutamylglutamic acid and the like. Preferred compounds of the invention are those wherein n represents the integer 1, i. e. those containing one glutamic acid or ester residue, and the invention will be described with particular reference thereto. The new compounds are generally well defined crystalline substance sparingly soluble in water and soluble in alcohol, ether and many other common organic liquids.

The compounds are useful as intermediates in the preparation of certain compounds of the group generally referred to broadly as folic acids. Thus, as described and claimed in co-pending application Serial No. 41,886, now Patent Number 2,560,617, N-(p-toluenesulfonyl-p-aminobenzoyl)-glutamic acid can be reacted with allyl bromide to form N-(N-(allyl)-p-toluenesulfonyl-p-amino-benzoyl)-glutamic acid. The allyl group of the latter compound can be saturated with bromine and the dibromoallyl compound then reacted with 2,4,5-triamino-6-hydroxypyrimidine to form a product which, upon removal of the p-toluenesulfonyl group with hydrogen bromide and a bromine acceptor by the procedure described and claimed in a concurrently filed, co-pending application, Serial No. 41,883, now Patent Number 2,562,222, yields an N- (N ((2 amino 4 hydroxy 6 pteridyl)methyl) paminobenzoyl)-glutamic acid (pteroylglutamic acid) generally recognized as being identical with the L. casei factor or vitamin Bc from liver. The compounds of the invention are also of value as intermediates in other methods for synthesizing members of the folic acid and related groups of compounds.

Compounds similar to or identical with those of the folic acid group made by using the intermediates or method of the invention, such as pteroylglutamic acid and pteroylgamma-glutamyl-gamma-glutamylglutamic acid, which are of greatest value as measured by their biological activity against Laczo-bacillus casei or Streptococcus fecalis R, are those wherein the glutamic acid residues possess the same configuration as l(+)-glutamic acid and for this reason the preferred compounds of the invention are those having the same configuration. However, the invention also contemplates compounds having the dextro configuration as well as racemic mixtures.

Compounds of the generic Formula I are of particular value because of the protection afiorded the aromatic amino group by the arylsulfonyl group. Compounds having the amino group thus protected are often not subject to decomposition and the formation of by-products when employed as a reactant to nearly the same extent as are compounds containing an unprotected amino group. Following the carrying out of a reaction using a compound containing such an arylsulfonylamino group, the arylsulfonyl radical can, as mentioned previously, be split readily from the molecule formed by treating the compound with hydrogen bromide in an acetic or other aliphatic acid medium and in the presence of a bromine acceptor, such as phenol, to prevent bromination of the amine formed. The compounds of the invention can also be converted to other similar compounds wherein Z is hydrogen by splitting the arylsulfonyl radical from the molecule in the manner just described. It should be mentioned, furthermore, that the methods involved in the present invention can be carried out and corresponding compounds prepared using compounds wherein the arylsulfonyl group is replaced by an alkylsulfonyl, aralkylsulfonyl or cycloalkylsulfonyl group, such as the methanesulfonyl, alpha-toluenesulfonyl or cyclohexylsulfonyl groups, respectively.

| z umnououzomomnon II III N- (arylsulfouyl-p-aminobenzoyl)glutamic acid compound I Arylsull'onyl halide mrrOoomudnomomoonom N- (p-amlnobenzoyD-glutamic acid compound The N'-(arylsulfonyl-p-aminobenzoyl)-glutamic acid compounds of the invention can be prepared readily, as illustrated in the accompanying diagram wherein R, n and Z have the values previously given, by reacting a glutamic acid compound, i. e., glutamic acid or a gamma-glutamylglutamic acid an alkyl ester thereof having the Formula II with an arylsulfonyl-p-aminobenzoyl halide having the Formula III. The halides referred to in this connection are the chlorides and bromides. Although a desired N'- (arylsulfonyl-p-aminobenzoyl)glutamic acid, or alkyl ester thereof, is preferably prepared starting with a glutamic acid compound which is itself an acid or alkyl ester, respectively, it should be noted that the esters of the invention can be hydrolyzed readily to the free acids, e. g. by warming with an aqueous alkali, and the free acids can be esterified, e. g. by warming with an alkanol and an esterification catalyst, such as hydrogen chloride.

The reaction of an arylsulfonyl-p-aminobenzoyl halide with glutamic acid or its alkyl ester is carried out conveniently by subjecting a mixture of the substances to the action of a hydrogen halide acceptor to react with the hydrogen halide formed. Substantially any hydrogen halide acceptor can be employed which will react with the hydrogen halide formed and which is otherwise nonreactive with the reactants and reaction products. Suitable hydrogen halide acceptors include magnesium oxide,

sodium hydroxide, sodium bicarbonate, and tertiary amines, such as pyridine, quinoline, triethylamine and tributylamine, tertiary amines being preferred. One convenient mode of operation comprises mixing the arylsulfonyl-p-aminobenzoyl halide and the glutamic acid compound, e. g. in the form of its hydrochloride, with ethylene dichloride or other suitable organic liquid and then adding the hydrogen halide acceptor slowly at about C. or somewhat higher.

The arylsulfonyl-p-aminobenzoyl-glutamic acid compound can be recovered by filtering the mixture if necessary, e. g. to remove magnesium oxide, or by washing with water and aqueous sodium bicarbonate and diluting with a relatively large volume of petroleum ether. The product can be recrystallized from a mixture of ethylene dichloride and hexane or other suitable solvent.

The reaction of a glutamic acid compound, particularly of the free acids, with an arylsulfonyl-p-aminobenzoyl halide can also be carried out in an aqueous medium using a water-soluble, mild alkali, such as sodium bicarbonate, as the hydrogen halide acceptor. The reaction can be carried out conveniently at from about to about 80 C. The use of an excess of too strong an alkali and of excessive temperatures should be avoided to prevent hydrolysis in the case of esters; unless such hydrolysis is desired. The N'-(arylsulfonyl-p-arninobenzoyl)- glutamic acid can be recovered from the reaction mixture by acidifying and filtering the mixture. The product can be recrystallized from water or dilute ethanol.

It should be mentioned that the N-(arylsulfonyl-paminobenzoyl)-glutamic acid compounds can also be prepared from the corresponding N'-(p-aminobenzoyl)- glutamic acid compounds having the Formula IV by treating the latter with an arylsulfonyl halide and a hydrogen halide acceptor. The N-(p-aminobenzoyl)- glutamic acid compounds can be prepared in known fashion by reacting a glutamic acid Compound H with a p-nitrobenzoyl halide to form an N'-(p-nitrobenzoyl)- glutamic acid compound and reducing the latter, e. g. catalytically with hydrogen.

The conversion of an alkyl ester of an N'-(p-aminobenzoyl)-glutamic acid to an alkyl ester of an N-(arylsulfonyl-p-aminobenzoyl)-glutamic acid can be carried out by reacting the amino ester with an arylsulfonyl halide in an organic medium, such as ethylene dichloride or benzene, using pyridine, quinoline, tributyl amine, triethyl amine or other tertiary amine as an hydrogen halide acceptor, the trialkyl amines being preferred. An excess of the amine can be used as the reaction medium, if

desired. A wide range of reaction conditions can be employed, satisfactory results having been obtained by allowing the mixture to stand at from about 0 to about 100 C. for from several minutes to several hours. Following the reaction period, the mixture can be poured into water, in case an excess of a water-soluble amine is used as the reaction medium, whereupon the alkyl ester of N'-(arylsulfonyl p aminobenzoyl)-glutamic acid separates in crystalline form and can be recovered by filtering. In case a water-insoluble reaction medium is used, the mixture can be washed with water to remove amine hydrohalide, then with aqueous sodium bicarbonate and finally dried and diluted with petroleum ether. The product is thus generally recovered in crystalline form. The conversion of an N'-(p-aminobenzoyl)glutamic acid to an N-(arylsulfonyl-p'aminobenzoyl)glutamic acid is accomplished readily by mixing the acid and an arylsulfonyl halide with an aqueous alkali, such as sodium bicarbonate or sodium hydroxide, or with pyridine or other tertiary amine. The reaction proceeds rapidly and is usually complete in from about 0.5 to about 3.0 hours when carried out at a temperature of from about to about 90 C. Upon acidifying an aqueous solution of the reaction product, the N-(arylsulfonyl-p-aminobenzoyl)-glutamic acid is obtained in crystalline form.

Although the invention has been described in the case of ester compounds with particular reference to the ethyl esters, it is understood that other alkyl esters, such as the methyl, propyl, iso-propyl, butyl, tert.-butyl, hexyl, nonyl, and dodecyl esters, can be used'with equal facility, if desired. Although the invention is directed particularly, in the case of esters of the glutamic acid residues, to alkyl esters, the process of the invention can also be carried out and corresponding compounds prepared using other esters, such as the phenyl, tolyl, xylyl, cyclohexyl,

benzyl and many other aryl, aralkyl or cycloalkyl esters.

Substantially any arylsulfonyl chloride or bromide can be used in the process with the formation of the correspondthe N (arylsulfonyl p aminobenzoyl)-glutamic acid compound. Arylsulfonyl halides which can be used include benzenesulfonyl chloride, benzenesulfonyl bromide, p-toluenesulfonyl chloride, o-toluenesulfonyl chloride, naphthalenesulfonyl bromide, naphthalenesulfonyl chloride and many others. Due to its ready availability and to the characteristic formation of well defined crystalline compounds, p-toluenesulfonyl chloride is a preferred arylsulfonyl halide, but the invention is not limited thereto.

Attention is again directed to the fact that, although the invention has been described with particular respect to the use of glutamic acid or its alkyl esters as starting materials, there can also be used other aminobenzoylglutamic acid compounds wherein from two to seven glutamic acid or ester residues are connected by peptide linkages involving the gamma-carboxyl groups.

Certain advantages of the invention are apparent from the following examples which are given by way of illustration only and are not to be construed as limiting.

Example 1 .Diethyl N p-nitrobenzoyl )-l-g/utamnte One hundred eleven grams of p-nitrobenzoyl chloride was added at about 0 C. over a period of about one hour to a solution of 95.8 grams of crude diethyl l(+)- glutamate hydrochloride and 80 milliliters of pyridine in 200 milliliters of benzene. The mixture was stirred for five hours, extracted first with dilute hydrochloric acid and then with aqueous sodium bicarbonate and the benzene removed under reduced pressure. The residue consisted of grams of a pasty, neutral fraction consisting largely of diethyl N'-(p-nitrobenzoyl)-l-glutamate. After recrystallization from dilute ethanol, the ester melted at 93 to 95 C. It had a specific rotation of (a)D =.l8 in 95 per cent ethanol. The sodium bicarbonate extract uprn acidification yielded 42 grams of p-nitrobenzoic act Example 2.Diethyl N p-aminobenzoyl -l-glutamnte Crude diethyl N'(p-nitrobenzoyl)-l-glutamate prepared as in Example 1 was dissolved in ethanol and reduced with hydrogen under a pressure of 40 pounds per square inch using platinum oxide as a catalyst. The mixture was then filtered to recover platinum and the ethanol evaporated under reduced pressure. There was thus obtained a 52 per cent yield of diethyl N(p-aminobenzoyl)-l-glutamate melting at to 138 C. Upon recrystallization from dilute ethanol, the ester melted at 140 to 141 C. and had a specific rotation of (a)D =9.5 in 95 per cent ethanol.

Azmlysis.-Calcd. for C16H2205N2: C, 59.6; H, 6.9; N, 8.7. Found: C, 59.6; H, 6.8; N, 9.0.

Example 3.N'-(p-nitr0benz0yl)-l-glutamic acid Eighteen and one-half grams of p-nitrobenzoyl chloride was added over a period of 0.5 hour to a solution prepared by dissolving 18.5 grams of l(+)-glutamic acid hydrochloride in a suspension of 42 grams of sodium bicarbonate in 200 milliliters of water. After stirring at 40 to 45 C. for two hours, the solution was filtered,

acidified and extracted with ether. The ether was evaporated and the residue crystallized from water. There was thus obtained 19.6 grams of N'-(p-nitrobenzoyl)-lglutamic acid melting at 110 to 114 C. andhaving a specific rotation of (a)D =9.0 in 95 per cent ethanol. Esterification of the acid with ethanol and hydrogen chloride gives the diethyl ester of Example 1.

Example 4 .-N p-am irzobenzoyl -l-glulamic acid Example 5 .Diethyl N p-t0luenesulfonyl-p-aminobenzoyl) -l-glutamate A mixture of 407 grams of p-toluenesnlfonyl-p-aminobenzoic acid and 3,450 milliliters of toluene was dried by distilling the mixture until 350 milliliters of distillate had been collected. A few drops of pyridine and 50 milliliters of thionyl chloride was then added to the 'dry toluene solution and the mixture stirred and refluxed for one-half hour. The solution was then cooled with agitation for two hours and the solid which precipitated was recovered by filtering and washing with toluene and then with mixed hexanes and drying. There was thus obtained 387 grams of p-toluenesulfonyl-p-aminobenzoyl chloride melting at 141 to 142 C.

A mixture of 48 grams of diethyl l(+)-glutamate hydrochloride, 68 grams of p-toluenesulfonyl-p-aminobenzoyl chloride, 19 grams of magnesium oxide, 250 milliliters of ethylene dichloride and 100 milliliters of water was stirred with cooling for about 4 hours. The mixture was filtered and the organic layer was separated from the filtrate and washed successively with water, ice cold dilute hydrochloric acid, water and dilute aqueous sodium bicarbonate. The washed organic layer Was then dried and diluted with mixed hexanes until slightly turbid and allowed to crystallize. Upon filtering the mixture, there was obtained 78 grams of diethyl N-(p-toluenesulfonylp-amino-benzoyl)-l-glutamate melting at 125 to 126 C. and having a specific rotation (a) ,=13.2 in a mixture of 5 per cent methanol, and 95 per cent of 95 per cent ethanol. The diester is hydrolyzed readily with dilute sodium hydroxide to form 1 (p-toluenesulfonyl-p-aminobenZoyl) -l-glutamic acid.

In similar manner using benzenesulfonyl bromide, o-toluenesulfonyl bromide or naphthalenesulfonyl chloride in place of p-toluenesulfonyl chloride there is formed diethyl N'- benzenesulfonyl-p-aminobenzoyl glutamate, diethyl N-(o-toluenesulfonyl-p-aminobenzoyl)glutamate or diethyl N- (naphthalenesulfonyl p aminobenzoyl)- glutamate, respectively. The corresponding free acids are formed in similar manner using glutamic acid or its hydrohalide in place of the diethyl ester. In like manner, also, p-toluenesulfonyl-p-aminobenzoyl chloride is reacted with gamma-glutamylglutamic acid, gamma-glutamylgamma-glutamyl-glutamic acid or their esters to form N-(p-toluenesulfonyl p aminobenzoyl) gamma-glutamylglutamic acid, N'-(p-toluenesulfonyl-p-aminobenzoyl)-gamma-glutamyl-gamma-glutamylglutamic acid or their esters, respectively.

Example 6.Diethyl N'-(p-toluenesulfonyl-p-aminobenz0yl)-l-glutamate A mixture of 0.95 gram of p-toluenesulfonyl chloride, 1.61 grams of diethyl N'-(p-aminobenzoyl)-l-glutamate and 4 milliliters of pyridine was warmed at 80 C. for about 30 minutes. Upon diluting the mixture with water, crystals of diethyl N'-(p-toluenesulfonyl p aminobenzoyl)-l-glutamate separated. The crystals were recovered by filtering and after drying weighed 1.3 grams. After recrystallization from dilute ethanol, the product melted at 125 to 126 C.

Analysis.Calcd. for C2sH2aO'7N2S: C, 58.0; H, 5.9; N, 5.9; S, 6.7. Found: C, 58.0; H, 5.9; N, 6.1; S, 6.9.

Example 7.-Diethyl N p-toluenesulfonyl-p-aminobenz0yl)-glutamate Thirty and nine-tenths grams of p-toluenesulfonyl-paminobenzoyl chloride and 23.9 grams of diethyl 1(+)- glutamate hydrochloride were dissolved in 300 milliliters of ethylene dichloride and the solution cooled to between 0 and C. The cold solution was stirred vigorously and 22.3 grams of triethylamine in 72 milliliters of ethylene dichloride was added slowly over a period of about 20 minutes. The temperature of the mixture Was held between 10 and 20 C. during the addition of the triethylamine and the mixture then allowed to stand at room temperature for one hour. The mixture was then washed successively with water, dilute hydrochloric acid, saturated aqueous sodium bicarbonate and finally with water. The colorless solution thus obtained was dried with anhydrous sodium sulfate and naphtha was added until the solution became opalescent. The mixture was thencooled to cause crystallization and filtered. The crystals, after drying, consisted of 36 grams of diethyl N'-(p-toluenesulonyl-p-aminobenzoyl)-1-glutamate melting at 124 to Example 8.N'-(p-toluenesulfonyl p aminobenzoyD-lglutamic acid A solution of diethyl-N'-(p-toluenesulfonyl-p-aminobenzoyl)-l-glutamate in dilute alcoholic sodium hydroxide was refluxed for ten minutes. The solution was then cooled and acidified and the white crystals which formed were recovered by filtering and recrystallized from water. The somewhat impure N'-(p-toluenesulfonyl-p-aminobenzoyl)-l-glutamic acid thus obtained melted at 99 to C.

We claim:

1. A compound having the general formula H-ITTQC ONHCHCHzCHzC 0 OR COOR wherein R is selected from the group consisting of hydrogen and alkyl radicals containing from one to twelve carbon atoms, inclusive, and wherein Z is an arylsulfonyl radical the aryl group of which contains from six to ten carbon atoms, inclusive, which includes the step of mixing an arylsulfonyl-p-aminobenzoyl halide, wherein the aryl group is as specified above, with a glutamic acid compound having the formula:

wherein R is as specified above, in the presence of a base, which is non-reactive with the other ingredients of the mixture, in suflicient quantity to react with the hydrogen halide formed.

6 The process of claim 5 wherein the base is a tertiary amine.

7. A process for the production of diethyl N'-(p-toluenesulfonyl-p-aminobenzoyl)glutamate which comprises mixing diethyl glutamate with p-toluenesulfonyl-p-aminobenzoyl halide, in the presence of a base, which is nonreactive with the other ingredients of the mixture, in sufiicient quantity to react with the hydrogen halide formed, to produce diethyl N'-(p-toluenesulfonyl p aminobenzoyl glutamate.

8. A process for the production of diethyl N'-(p-toluenesulfonyl-p-aminobenzoyl)-glutamate which comprises mixing, with agitation, diethyl glutamate with p-toluenesulfonyl-p-aminobenzoyl halide, in the presence of magnesium oxide in sufiicient quantity to react with the hydrogen halide formed, water, and a water-immiscible solvent, and separating diethyl N-(p-toluenesulfonyl-paminobenzoyl)-glutamate from the reaction mixture.

References Cited in the file of this patent UNITED STATES PATENTS Name Date Angier June 6, 1948 Boothe et a1 Oct. 3, 1950 OTHER REFERENCES Number Suter: Organic Chem. of Sulfur (1944), Wiley, pp.

Williams: J. Biol. Chem, vol. 156, pp. 85-89 (1944). Degering: An Outline of Organic Nitrogen Compounds, University Lithoprinters, Ypsilanti, Michigan, 1945, p. 238, paragraph 4. 

1. A COMPOUND HAVING THE GENERAL FORMULA 